Generally, gas turbine engines have three main sections or assemblies, including a compressor assembly, a combustor assembly, and a turbine assembly. In operation, the compressor assembly compresses ambient air. The compressed air is channeled into the combustor assembly where it is mixed with a fuel and ignites, creating a heated working gas. The heated working gas is expanded through the turbine assembly. The turbine assembly generally includes a rotating assembly comprising a centrally located rotating shaft and a plurality of rows of rotating blades attached thereto. A plurality of stationary vane assemblies, each including a plurality of stationary vanes, are connected to a casing of the turbine assembly and are located interposed between the rows of rotating blades. The expansion of the working gas through the rows of rotating blades and stationary vanes in the turbine assembly results in a transfer of energy from the working gas to the rotating assembly, causing rotation of the shaft. The shaft further supports rotating compressor blades in the compressor assembly, such that a portion of the output power from rotation of the shaft is used to rotate the compressor blades to provide compressed air to the combustor assembly.
With increasing improvements in compressor efficiency and the compression ratio, the temperature of the compressed air exiting the compressor to the combustor assembly has increased. For example, in gas turbine engines being developed for use in stationary power plant applications, the compression ratio of air passing though the compressor may be on the order of 30:1, and may have discharge temperatures of approximately 550° C.
Current combustor assemblies have typically been designed to receive air at temperatures of up to approximately 450° C. An increase in the temperature of the incoming compressed air, such as up to 550° C., could cause the material of a compressor/combustor case for the combustor assembly to exceed its creep and strength limits. Hence, an increase in the case temperature could require specification of higher temperature materials, such as nickel based alloys, for the compressor/combustor case, resulting in increased costs for the production and maintenance of the combustor assembly.